The subject application is related to subject matter disclosed in Japanese Patent Application No. Hei 11-262711 filed on Sep. 16, 1999 in Japan to which the subject application claims priority under the Paris Convention and which is incorporated by reference herein.
1. Field of the Invention
The present invention relates to semiconductor device manufacturing apparatuses employing a PVD method, such as sputtering apparatuses and vacuum evaporation apparatuses. In particular, the present invention relates to a multicathode sputtering apparatus capable of reducing the cleaning frequency of filters, the filters themselves, a filtering frame, a semiconductor device manufacturing method, and a semiconductor device manufacturing apparatus.
2. Description of the Related Art
In the field of semiconductor devices, ground rules are becoming finer and the number of interconnection layers is increasing, to increase the aspect ratio (depth to diameter) of each via hole. As a result, a standard sputtering technique finds difficulty to fill such high-aspect-ratio via holes. To cope with this problem, there is a long-throw sputtering technique that elongates the distance between a target and a substrate and forms a film on the substrate only with particles that are straightly sputtered from the target toward the substrate. This technique is capable of correctly forming films in via holes and securing a sufficient coverage of each film. This technique, however, has a problem of causing asymmetry among films in via holes located along the periphery of a substrate and a problem of hardly forming a uniform film over the surface of a substrate. The larger the diameters of substrates or silicon wafers, the more the problems of asymmetry and unevenness become serious. To solve these problems, Japanese Unexamined Patent Publications Hei 10-121235 and Hei 11-29859 propose a multicathode sputtering apparatus that arranges a plurality of cathodes and corresponding targets in a chamber. This apparatus employs filters that pass only vertically oriented particles to form a film on a substrate, thereby improving the overall uniformity of the film.
FIG. 1 shows a film forming state of a multicathode sputtering apparatus according to a prior art. A chamber 5 accommodates targets 41 to 43 that are attached to cathodes, respectively. The targets 41 to 43 face a substrate 8 with filters 71 to 73 interposing between them. The filters 71 to 73 have openings corresponding to the targets 41 to 43, respectively. The diameter of each opening is greater than the diameter of the target. The chamber 5 has an outlet 6 connected to a vacuum pump (not shown).
To form a film on the substrate 8, the chamber 5 is evacuated to a predetermined pressure, and argon gas is introduced into the chamber 5 through an inlet 7 to a sputtering pressure. Power sources 61 to 63 apply predetermined power to the cathodes to produce plasma on the targets 41 to 43 to sputter particles from the targets 41 to 43. The sputtered particles pass through the openings of the filters 71 to 73 and deposit on the substrate 8.
The sputtered particles linearly advance from the targets 41 to 43 according to the cosine rule at any angles with respect to normal lines extended from the targets. Particles of large angles hit and deposit on the filters 71 to 73 without reaching the substrate 8. Only geometrically reachable particles arrive at the substrate 8 and deposit thereon to form a film, thereby suppressing overhangs on steps and via holes, improving the coverage of the film over the substrate 8, and eliminating asymmetry in the film. By individually changing the power to the cathodes, the uniformity of a film on the substrate 8 may be improved.
This prior art, however, deposits particles around the openings of only the filter 71 that is closest to the cathodes, among the filters 71 to 73. When the particles on the filter 71 exceed a certain thickness, they peel off the filter 71 and drop onto the substrate 8, to form clusters of particles on the substrate 8. To avoid this, the prior art must frequently wash the filter 71, which deteriorates the mean time between maintenances of the apparatus. The peeling problem frequently occurs when forming titanium nitride (TiN) films or tantalum nitride (TaN) films, to greatly deteriorate productivity.
An object of the present invention is to provide a filter capable of minimizing particles depositing thereon.
Another object of the present invention is to provide a filter capable of preventing particles peeled off the same from dropping onto a substrate.
Still another object of the present invention is to provide a filtering frame capable of minimizing particles depositing thereon.
Still another object of the present invention is to provide a filtering frame capable of preventing particles peeled off the same from dropping onto a substrate.
Still another object of the present invention is to provide a semiconductor device manufacturing apparatus capable of minimizing particles depositing on filters.
Still another object of the present invention is to provide a semiconductor device manufacturing apparatus capable of preventing particles peeled off filters from dropping onto a substrate.
Still another object of the present invention is to provide a semiconductor device manufacturing method capable of minimizing particles depositing on filters.
In order to accomplish the objects, a first aspect of the present invention provides a filter having a flat plate with circular openings and a funnel provided for each of the openings. Each funnel has a bottom opening matching with the plate opening and a top opening smaller than the bottom opening. A normal line extended from the center of the top opening coincides with a normal line extended from the center of the bottom opening and is in parallel with a normal line extended from the plate. Sputtered particles deposit on an outer face of each funnel. Since sputtered face is wide, the deposited particles spread into a thin film. This elongates a time to cause the peeling of the film off the funnels, prevents the formation of clusters of particles on a substrate, and extends the life of the filter. Even if the film on the funnels peels off, it will stay on the filter because the peeled film is unable to go beyond the funnels. Accordingly, no peeled film drops onto the substrate. Each funnel passes particles sputtered from only an overhead target and blocks particles sputtered from adjacent targets. This improves the directivity of sputtered particles to form a uniform film on the substrate. For each funnel, particles sputtered from adjacent targets except an overhead target hit the outer face of the funnel substantially at a right angle, and therefore, the particles deposited on the funnel strongly adhere thereto and hardly peel off.
According to the first aspect, the bottom openings of adjacent funnels may partly overlap one another, and the overlapping parts of the adjacent funnels may be cut. This arrangement enables the distance between adjacent targets to be freely set without regard to the dimensions of the funnels.
According to the first aspect, the flat plate may be a flat disk so that the filter may easily be rotated in a sputtering apparatus to improve the uniformity of a film formed on a substrate.
A second aspect of the present invention provides a filtering frame having a first filter made of a flat plate having first circular openings, and a second filter that is in parallel with the first filter and has second circular openings corresponding to the first openings, respectively, the diameter of the second openings being smaller than that of the first openings, normal lines extended from the centers of each pair of the first and second openings coinciding with each other. The filtering frame is installed in a sputtering apparatus such that the first filter is closer to cathodes than the second filter. With this arrangement, the first and second filters may uniformly catch sputtered particles, to increase the number of substrates processible before the particles caught by the filters start to peel off and extend the washing intervals of the filters.
According to the second aspect, the first and second filters may be disks having the same diameter with normal lines extended from the centers of the filters coinciding with each other. The filtering frame is rotatable in a sputtering apparatus, to form a uniform film on a substrate from sputtered particles.
According to the second aspect, the filtering frame may further have a third filter opposing to the first filter with the second filter interposing between them. The third filter has third circular openings corresponding to the second openings, respectively. The diameter of the third openings is smaller than that of the second openings. Normal lines extended from the centers of each pair of the second and third openings coincide with each other. Particles caught by the first to third filters are uniformly distributed among them, to further increase the number of substrates processible before the particles caught by the filters start to peel off.
According to the second aspect, the first filter may have first funnels. The first funnels are provided for the first openings, respectively, and have each circular top and bottom openings. The bottom opening is larger than the top opening, is equal to the first opening, and is fitted to the first opening. Normal lines extended from the top, bottom, and first openings coincide with one another. The second filter may have second funnels. The second funnels are provided for the second openings, respectively, and have each circular top and bottom openings. The bottom opening is larger than the top opening, is equal to the second opening, and is fitted to the second opening. The top opening of the second funnel is smaller than the top opening of the first funnel. Normal lines extended from the top and bottom openings of a pair of the first and second funnels coincide with one another. Sputtered particles deposit on the first and second funnels and spread into thin films. This results in elongating a time to cause the peeling of the thin films off the funnels, preventing clusters of particles to be formed on a substrate, and extending the lives of the filters. Even if the films peel off, they hardly go beyond the funnels. Namely, the peeled films may stay on the filters and may not drop onto a substrate. Each funnel passes particles sputtered from an overhead target and blocks particles sputtered from adjacent targets. This improves the directivity of sputtered particles to form a uniform film on a substrate. For each funnel, particles sputtered from adjacent targets except an overhead target hit the outer face of the funnel substantially at a right angle, and therefore, the particles deposited on the funnel strongly adhere thereto and hardly peel off. The openings on the filters are gradually scaled down from those on the filter closest to cathodes toward those on the filter farthest from the cathodes, to uniformly distribute caught particles among the filters. This improves the number of substrates processible before the particles caught by the filters start to peel off.
A third aspect of the present invention provides a semiconductor device manufacturing apparatus. The apparatus has a vacuum chamber, cathodes arranged in the vacuum chamber, disk targets arranged on the bottoms of the cathodes with the bottoms of the targets being flush with a plane, and at least two filters arranged under the targets. Each of the filters has openings corresponding to the targets, respectively, and being flush with a plane that is in parallel with the plane the targets are flush with, the diameters of the openings being decreased in order of the distances of the filters from the targets. Namely, the diameters of the openings on the filters gradually become smaller as they are separated from the cathodes. As a result, particles caught by the filters are uniformly distributed among the filters, to increase the number of substrates processible before the particles on the filters start to peel off, compared with the prior art that employs openings of the same diameter. The third aspect, therefore, extends the washing intervals of the filters.
According to the third aspect, the semiconductor device manufacturing apparatus may consist of a vacuum chamber, cathodes arranged in the chamber, disk targets arranged on the bottoms of the cathodes with the bottoms of the targets being flush with a plane, and the filtering frame of the second aspect arranged in the chamber such that normal lines extended from the centers of a pair of the first filter opening and target bottom coincide with each other. According to this arrangement, a surface extended from a given funnel converges at a point and diverges from the point toward an overhead target without intersecting with the overhead target. The xe2x80x9csurface extended from a given funnelxe2x80x9d forms a first cone starting from the given funnel and then forms an inverted second cone starting from the apex of the first cone. The funnels on the filters are so angled as to catch sputtered particles on the target side of each filter. Namely, no sputtered particles are caught by the bottom face of each filter, and there is no films peeling off the bottoms of the filters.
According to the third aspect, the diameters of the openings may be larger than the diameter of the targets. This arrangement reduces particles to be caught by the filters and increases the number of substrates processible before the particles caught by the filters start to peel off.
According to the third aspect, the cathodes may be fixed to the bottom of a rotatable head. The head may be fixed to the filters. This arrangement rotates the targets and filters to form a uniform film on a substrate.
A fourth aspect of the present invention provides a semiconductor device manufacturing method including the steps of pumping a chamber, introducing argon gas into the chamber, applying power to cathodes to generate argon or metal ion plasma under targets, producing a source flow from particles sputtered from the targets by the plasma, separating a first branch from the source flow through the use of a first filter, the first branch forming a first film on the first filter, separating a second branch from the source flow through the use of a second filter, the second branch forming a second film on the second filter, the thickness of the second film being substantially equal to that of the first film, and directing the source flow passed through openings of the second filter toward a semiconductor substrate to form a third film on the substrate. This method evenly distributes particles caught by the filters among the filters, to increase the number of substrates processible before the particles caught by the filters start to peel off. Namely, the fourth aspect is capable of reducing the washing intervals of the filters.
During the step of depositing the third film on the substrate, the fourth aspect may rotate a head to which the targets and first and second filters are fixed. This may improve the uniformity of the third film.
Other and further objects and features of the present invention will become obvious upon an understanding of the illustrative embodiments about to be described in connection with the accompanying drawings or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employing of the invention in practice.